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Oxic microshield and local p H enhancement protects Z ostera muelleri from sediment derived hydrogen sulphide
Author(s) -
Brodersen Kasper Elgetti,
Nielsen Daniel Aagren,
Ralph Peter J.,
Kühl Michael
Publication year - 2015
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13124
Subject(s) - rhizosphere , biogeochemical cycle , water column , botany , rhizome , environmental chemistry , seagrass , photosynthesis , meristem , chemistry , sediment , biophysics , biology , shoot , ecology , ecosystem , paleontology , genetics , bacteria
Summary Seagrass is constantly challenged with transporting sufficient O 2 from above‐ to belowground tissue via aerenchyma in order to maintain aerobic metabolism and provide protection against phytotoxins. Electrochemical microsensors were used in combination with a custom‐made experimental chamber to analyse the belowground biogeochemical microenvironment of Z ostera muelleri under changing environmental conditions. Measurements revealed high radial O 2 release of up to 500 nmol O 2 cm −2 h −1 from the base of the leaf sheath, maintaining a c . 300‐μm‐wide plant‐mediated oxic microzone and thus protecting the vital meristematic regions of the rhizome from reduced phytotoxic metabolites such as hydrogen sulphide (H 2 S). H 2 S intrusion was prevented through passive diffusion of O 2 to belowground tissue from leaf photosynthesis in light, as well as from the surrounding water column into the flow‐exposed plant parts during darkness. Under water column hypoxia, high belowground H 2 S concentrations at the tissue surface correlated with the inability to sustain the protecting oxic microshield around the meristematic regions of the rhizome. We also found increased p H levels in the immediate rhizosphere of Z. muelleri , which may contribute to further detoxification of H 2 S through shifts in the chemical speciation of sulphide. Zostera muelleri can modify the geochemical conditions in its immediate rhizosphere, thereby reducing its exposure to H 2 S.